Earth borehole logging system



Feb. 9, 1960 J. J. ARPS EI'AL 2,924,432

. EARTH BOREHOLE LOGGING SYSTEM Filed lay a, 1956 v 2 Sheets-Sheet 1 J.J. ARPS ET AL EARTH BOREHOLE LOGGING SYSTEM 2 Sheets-Sheet 2 Filed May8, 1956 United States Patent EARTH BOREHOLE LOGGING SYSTEM Jan J. Arps,Dallas, Tex., and Serge A. Scherbatskoy, Tulsa, Okla.

Application May 8, 1956, Serial No. 583,503

7 Claims. (Cl. 255-1) This invention relates to logging systems used forprocuring and registering or recording information concerning one ormore physical characteristics exhibited at relatively inaccessiblelocations in earth boreholes; and more particularly, to means forsecuring for logging purposes any of a group of one or more types ofinformation, selectively and at will and at a desired time, duringeither continuance of actual drilling of the borehole or a period ofsuspension of drilling. Still more specifically, the invention relatesto a borehole logging system including means for operating apparatusused for securing desired information from within an earth borehole, atonly such times during continued drilling of the borehole or duringsuspension of drilling, as may be desired; and at the will of theoperator, without interference with any of the normal drilling procedureand apparatus.

It has been proposed previously to convey information obtained byinstruments situated at an inaccessible location within an earthborehole, to an accessible operating point outside the borehole, byemploying as informationrepresenting signals, temporary pressure changescreated in the downwardly flowing stream of drilling fluid in a drillstring. The signals in the previously proposed system were relativelycontinuously transmitted under the controlling action of automatic timeror like means comprised in instrumentation housed in a part of the lowerend of a drill string. No manual or operator control over the operationof the information-obtaining and signaltransmitting means was possible.That apparatus was either manually set in operation when at the surface,or later by operation of an automatic pressure-sensitive switch meansactuated by static pressure of the well fluid upon lowering of the drillstring into the well, and/or circulation of drilling fluid. Examples ofthe previously proposed type of logging system are disclosed incopending applications Serial No. 414,381, filed March 5, 1954; SerialNo. 431,734 filed May 24, 1954, and Serial No. 489,537 filed February21, 1955, to which reference may be made in respect to certain detailsof apparatus and operation. Due to the high cost of batteries of a typesuitable for operation in the high-temperature environment near thebottoms of deep earth boreholes, and to the loss in battery lifeoccasioned by operation of logging apparatus during running-in of thedrill string and during non-drilling periods, it is desirabe to providemeans whereby the apparatus at the lower end of a drill string may beoperated or rendered inoperative, at the option of the operator at theoperating point outside the borehole. Further, it is desirable that thiscontrol may be accomplished without interruption of drilling. Theprovision of some such remote control means would permit effectivebattery life to be greatly extended, and would permit a greaterflexibility of operation in respect to any given channel of logginginformation in a multi-channel system. For example, in a system in whichsuch physical characteristics as earth resistivity, natural potential,bit temperature, and bit wear are to be logged, it might at times bedesirable to log only resistivity over an extended 2,924,432 PatentedFeb. 9, 1960 ice ' period, with only an occasional check on bit wear andbit temperature. In the previously proposed systems, each channel ofinformation or type of characteristic measurement was presented in itsrespective time position in a cyclical or time-multiplex procedure, oncefor each operations cycle, irrespective of the relative momentary valueof the information.

In view of the preceding considerations, it is a prime object of thepresent invention to provide a borehole logging system in which theinformation obtaining and signaling apparatus located in a borehole ator near the lower end of a drill string may be activated, or its actionsuspended, by an operator outside the borehole, without any electricalconnections between the two places and without interruption of drilling.

Another object of the invention is to provide a borehole logging systemin which any desired one of a plurality of types of informationobtainable at an inaccessible location adjacent the lower end of a drillstring in a borehole may selectively be obtained by means under controlof an operator outside the borehole.

Another object of the invention is to provide a logging system of thetype indicated in which battery power consumption is restricted todesired intervals of time under control of an operator outside theborehole being logged.

An additional object of the invention is to provide a logging system foruse during rotary drilling of an earth borehole, in which operation ofinformation-obtaining and signaling apparatus at the lower end of adrill string is under direct control of an operator at a surfacelocation outside the borehole.

The aforestated objects and other objects and advantages hereinaftermade apparent are attained in a preferred type of system by provision ofapparatus including means sensitive to a pressure differential at theinaccessible location in a drill string in a borehole, which pressuredifferential sensitive means is arranged to control activation anddeactivation of information-obtaining and signaling means in response toone or more shortduration reductions in drilling fluid back pressureproduced by temporary reduction of drilling fluid flow. Thepressure-sensitive means is arranged to be in hydraulic communicationwith the downwardly flowing drilling fluid stream in the drill stringand the upwardly flowing return stream outside the drill string, and isadapted to move a control linkage member in one direction in response toa reduction, from normal back pressure in the drill string at thesubsurface location and in the opposite or return direction in responseto return of the stream back pressure to normal value. The controllinkage member is arranged to operate a step-by-step means which atsuccessive steps alternately closes and opens a power supply circuitleading to the information-obtaining and signaling means, or atsuccessive steps of a series closes individual operating circuits andsteps to a neutral attitude or position at which the operating circuitsare all left in open-circuit (inoperative) condition.

The preferred type of system comprises apparatus diagrammaticallyillustrated in the accompanying drawings, in which:

Figure l is an illustration showing environmental and other features ofthe system of the invention as applied to logging operations conductedduring drilling of an oil well, and illustrating in some detail certainapparatus components at a surface operating location, and a drill stringin a borehole penetrating formations of the earth;

Figure 2 is a diagrammatic view indicating relative locations ofapparatus components in a part of the drill string shown in Figure 1;

Figure 3 diagrammatically illustrates the mechanical and electricalfeatures of a system in which a single subject of investigation is to belogged; and

Figure 4 is an illustration similar to that of Figure 3 but relating to.apparatus for handling several subjects of investigation to be logged.

Referring now to the drawings and to Figure 1 in particular, an earthborehole is shown penetrating a surface earth formation 12 and aplurality of formations therebelow, the borehole having been drilled bymeans including drill string designated generally by numeral 14 andterminated at its lower end by a bit 16. The drill string comprises adrill collar 18 normally situated at an inaccessible location in theborehole as indicated, and a plurality of tubular drill pipe sectionssuch as 20, to the lowermost of which the drill collar is secured. Thedrill string comprises at its upper end a tubular kelly 22 which isadapted to be rotated by a rotary table 24 through which the kellyslidably extends. The rotary table is rotatable by power means includinggearing as illustrated or as may be well known in the art. The kelly isrotatably supported by a swivel 26 which serves also to conduct drillingfluid supplied through a hose 28, to the kelly 22. The swivel issupported and operated by means as indicated and which are well known inthe art and not per se of the present invention.

Drilling fluid under considerable pressure is supplied to hose 28through piping 30 by pump means which may comprise one or more unitssuch as pump 32. The fluid discharged from the pump may pass by orthrough a surge bell and through a valve 33 interposed in piping 30leading from the pump outlet. The pump is driven by a power unit 34having a throttle lever 35 or other operable means for controlling thespeed and the discharge rate of the pump. The pump draws drilling fluidfrom a supply tank or pit 36 through an intake pipe 37. Thus drillingfluid is supplied under pressure to the interior of the drill string,through which it flows downwardly in a stream for exit through orificesin the bit 16. The discharged fluid cleans the bit and carries upwardlythrough the borehole annulus encircling the bit, the rock chips removedby the bit; and the fluid and transported chips are discharged from theborehole through a lateral pipe 38 at the upper end or top of theborehole. Hence the drilling fluid is circulated by the pump inwardlythrough the drill string into the lower reaches of the borehole andthence outwardly in the borehole annular space (borehole annulus) aroundthe drill string, to the pin 36. The fluid, as it is forced throughpiping 30, is normally under considerable back pressure, there being alarge friction loss in the stream path through the drill bit. Thus thereis created a considerable pressure differential between adjacent pointsinside and outside the drill collar. When the pump 34 is slowed byreverse or throttling motion of control lever 35, however, the rate ofdischarge of the pump is lowered, and the back pressure andaforementioned pressure differential experience a corresponding drop invalue.

While reverse or throttling movement of pump control lever 35 has beendescribed as a means of temporarily reducing pressure differential orthe back pressure in the stream of drilling fluid in the drill string,it is clear that complete cessation of pumping would accomplish asimilar result; and the same effect may be attained by partial orcomplete closure of valve 33 during pumping of fluid. According to theinvention, such reduction in back pressure or the corresponding decreasein pressure differential in the drilling fluid stream inside and outsidethe drill collar, is employed as a means of effecting control ofinformation-securing and signaling apparatus located in the drillcollar, using apparatus hereinafter described.

Referring now to Figure 2, wherein bit 16 and drill collar 18 are shownin drilling position in borehole 10, the drill collar is shown with aportion removed to show an apparatus case 40 and a valve V positioned inrespective locations in the drilling fluid passage in the collar. Themeans and mode of positioning these elements in the drill collar may beas desired or as more particularly disclosed in one or more of theaforementioned applications. Valve V is preferably anelectromagnetically operated valve interposed in the drilling fluidpassage to alternately impede and free the flow of fluid therethrough toproduce temporary or short-duration pressure-rise signal pulses in thedrilling fluid stream, without appreciable reduction in the rate offluid flow, in a manner and for signaling purposes such as areillustrated and described in the mentioned applications. Apparatus case40 is fixed in the drill collar 18 so as to permit relatively free flowof fluid therepast, and is provided with hydraulic connections exposedto the downflowing fluid stream inside the drill collar and to theupflowing stream outside the drill collar for operating apparatus by thepressure differential between those two streams. Such apparatus and itsoperation are hereinafter described.

In Figure 3 there is indicated diagrammatically within dash-linerectangle 41, apparatus housed in case 40 in the drill collar andelectrically connected to the operating coil of valve V in a mannerindicated in the aforementioned applications. Within the apparatus case40 and hydraulically connected as indicated in Figure 2 by suitablefluid-tight tubing 44: to opening 400 in the case and by tubing 440 tothe upwardly flowing stream outside the drilling collar at 180, is apressure-sensitive means herein shown as comprising a fluid-tightcylinder 44 fixedly mounted in the case and a cooperating piston 44 on apiston rod 44r passing through sealed glands in the cylinder ends. Thuspiston 44p is made sensitive to the pressure differential between 400and 180. The piston is adapted, under all normal drilling fluid flowconditions in the drill collar and adjacent upwardly flowing stream, tobe forced downwardly to the position or attitude shown in Figure 4against the lifting influence of a tension spring 49, by the higherpressure of drilling fluid admitted to the upper end of the cylinderthrough tubing 44f. Downward movement of the piston is limited by meanspresently to be described. Pivoted to the upper end of piston rod 44r isa connector link 45 which at its opposite end is pivotally connected toa lever 46. Lever 46 is at its left end pivotally mounted on a fixedabutment 47 in case 40, and has intermediate its ends a stop 48 forcoaction with an upper fixed abutment 51 and a stop 48 adapted forcoaction with a lower fixed abutment 51, the abutments 51 and 51 beingsecured in any suitable manner in case 40 and acting to limit upward anddownward movement of the lever. A tension spring 49 has its upper endsecured to fixed structure in case 40 and its lower end to anintermediate portion of lever 46, the construction and arrangement beingthat when there is no appreciable pressure differential between points400 and spring 49 raises lever 46 to a position wherein stop 48 engagesfixed abutment 51. At its right end lever 46 is pivoted to a pawl 50which is stressed by a spring 52 in a direction to engage a ratchetwheel 53 which is secured to a shaft 54 mounted for rotation in suitableguides and bearings (not shown). Ratchet wheel 53 and pawl 50 are soproportioned and arranged that as piston 44p is forced downwardlyincident to creation of an appreciable pressure differential betweenpoints 400 and 180, pawl 50 is drawn downwardly and rotates ratchetwheel 53 an extent equal to one tooth space; and spring 49 isconcurrently tensioned. Such downward motion of lever 46 and pawl 50 islimited by engagement of stop 48' with abutment 51'. During thisrotation of ratchet wheel 53, a holding pawl 55, stressed by a tensionspring 56, rides idly over a complete tooth of the wheel and acts, underthe influence of spring 56, to engage the rear face of such tooth andhold the ratchet wheel and shaft 54 from retrogressive rotation.

Aifixed to shaft 54 for rotation therewith and thereby is a cam disc 57having alternating lobes 57a and depressions 57b, the total number oflobes and depressions being equal to the number of teeth comprised inthe rim of the ratchet wheel. Cam 57 has riding thereon a follower leverfollower lever is pivoted at one end to structure fixed in case 40, andspring 59 is anchored to such structure, as indicated. Lever 58 bears aninsulated contact 60 arranged for electrical cooperation with acushioned substantially stationary contact 61 mounted on insulated fixedstructure in case 40. To the contacts are secured respective insulatedconductors 60c and 61c as indicated. The arrangement of the step-by-stepcontroller means comprising the pawl, ratchet wheel, follower lever,contacts and subsidiary parts is such that in response to successivetemporary reductions in the pressure diflferential between openings 400and 180, contacts 60, 61 alternately open and close a circuit comprisingconductors 60c, 61c.

Conductors 60c, 61c and their respective contacts serve as means foractivating and de-activating electrical apparatus in aninformation-securing and operations unit 62, which is powered from asource of electric power herein represented as a battery 63. The powersource is connected to contact 60 and through contact 61 to unit 62 asindicated, and is such that when the contacts are closed, theinformation-securing apparatus in unit 62 is energized, information issecured, and means included in unit 62 and energized from the powersource acts to produce information-representing pulses of electriccurrent in a manner more fully described in one or more of theaforementioned applications. The information-representing electriccurrent pulses produced in unit 62 are translated into equivalentdrilling fluid pressure-increase signals for transmission to the surfacelocation outside the borehole, by means including theelectromagnetically operated valve V whose coil V0 is intermittentlyenergized by the electric current pulses. The current pulses areconducted to coil Vc through suitable conductors 65, 66 which areconnected to the apparatus in unit 62.

From the foregoing description it is evident that when follower lever 58is riding in a depression of cam 57, and contacts 60, 61 are open, theinformation-securing means is inoperative for lack of energization bybattery 63, and valve V will produce no temporary pressure-increasesignals in the drilling fluid stream. Under such conditions theapparatus is quiescent, or idle, and consumes no power. When it isdesired to obtain information that can be secured by the subsurfacemeans in the drill collar, the driller or operator temporarily reducesthe pressure differential at the lower end of the drill string byretarding control lever 35 (or operating valve 33) for a few seconds,and then returns the lever or valve to normal. In response to thetemporary reduction of back pressure at 400, piston 44;), lever 46 andpawl 50 are given an upward stroke by spring 49 and are then returned toinitial position by return of back pressure, causing rotation of wheel53 and cam 57 through one-sixth revolution. Thus contacts 60, 61 will beclosed, and unit 62 energized. Pressureincrease signal pulses will becreated in the drilling fluid stream in the drill collar above valve V,representing the information secured; and these signal pulses will bealmost instantly transmitted upwardly through the drilling fluid streamto the surface location. The manner in which the electric current pulsesand the corresponding pressureincrease pulses in the drilling fluidrepresent the informa tion gathered or secured by the apparatus in unit62 may be widely varied and the apparatus may be of any suitable type,or such as is disclosed in the mentioned copending applications.

The information-representing pressure change pulses transmitted from thesubsurface location are detected and translated at the surface locationby means including an electrically energized pressure-transducer unit 70(Figure 1) which is in hydraulic communication with the interior of pipe30 and is furnished electrical energy from a source of supply 71, all asindicated. The electrical output of transducer unit 70 is applied by wayof suitable conductors 72 to an amplifier unit 73 which may be furnishedpower from a supply 74. The amplified signal output of unit 73 isapplied to the pen unit 75p of a suitable graphical recorder 75, on thechart paper 750 of which the pen traces a graphical representation ofthe pressure pulse signals detected by the transducer unit. The graph75g indicates by excursions or deviations from normal, the durationsand/or time relationships of the pressure pulse signals arriving fromthe subsurface location, the chart paper being traversed under the penat a constant or predetermined rate by clockwork 76 or other suitablemeans as indicated or as described in one or more of the previouslymentioned applications.

With the subsurface equipment or apparatus in operation, the describedprocess of obtaining information at the surface as it is secured by thesubsurface means may be interrupted and the equipment rendered idle byagain inducing a pressure differential drop by operation of lever 35 orvalve 33 to temporarily out down the flow of drilling fluid, such actioncausing rotation of cam 57 to position a depression 57b under followerlever 58 and opening of contacts 60, 61. It is evident that successivetemporary reductions of drilling fluid flow or back pressure will causealternate activation and de-activation of the subsurface apparatus, andthat the periods of activity and of quiescence may readily be governedat the will of the driller or operator.

In Figure 4 there is diagrammatically depicted a form of apparatussimilar to that indicated in Figure 3 and usable in lieu of the latterwhen any of several different types or channels of information is to beselectively obtained. In this modified form of apparatus the signalingvalve V is unchanged, but is supplied informationrepresenting electriccurrent pulses from a unit 82 which contains a suitable source of powerand is connected to ground as indicated. The apparatus in unit 82 maycomprise an amplifier and/or other electrical conversion means, and issupplied with electrical currents or signals by way of a conductor 83and the ground connection indicated. The output of unit 82, when thatunit is in operation, is intermittent pulses of electric current ofsuitable duration, such as of from one to several seconds duration, asrequired for proper operation of valve V and as required forrepresentation of the information to be transmitted. Unit 82 is renderedactive, or inactive, by means operated by ratchet wheel 53 under controlof an operator at the surface location.

Secured to shaft 54 (Figure 4) which is rotated in intermittent steps byratchet wheel 53 in the manner and by means previously described, is arotary switch arm 84 which is, as the shaft is moved through successivesteps, successively positioned at successive stations and in contactwith a respective one of a series of circularly disposed stationaryinsulated contactsSO, S1, S2, S3, S4 and S5, there being as many of suchcontacts as there are teeth in ratchet wheel 53. One of the contacts(S0) is left blank, or not connected to any other apparatus, wherebywhen the switch arm is positioned at that station, theinformation-securing and signaling apparatus is de-energized and loggingvalues or intelligence is not gathered nor signals transmitted. Othersof the contacts, such as S1, S2, S3 and S4 in this example, areconnected by suitable conductors to respective informationderiving unitsU1, U2, U3 and U4, each of which, when connected to unit 82 by switcharm 84, is activated to derive or secure information of a particularsort or type. For example, unit U1 may be connected to an electrodesystem indicated diagrammatically as E1, and furnish electrical currentto unit 82 representing self potential of earth formations adjacent thelower end of the borehole. Similarly, unit U2 may be connected to anelectrode system represented by E2, and secure information concerningformation resistivity or other physical characteristic and furnishcurrent to unit 82 representative of the information. Unit U3 maycomprise, for example, means for securing measured values oftemperature, pressure, or other physical characteristic within the drillcollar or within the borehole. As many units U1, etc. are employed asthere are types or kinds of information which it is desired to obtain;and there are provided switch stations and contacts S1, etc. equal totwo more than the number of units U1, etc. Similarly, ratchet wheel 53is provided with as many teeth as there are switch stations. The switchstation or contact next preceding station or contact S0, and here shownas S5, is connected to a special identification signal-generating unit85, which, when rendered active by connection to unit 82, provides thelatter unit with a distinctive electric signal current which causes unit82 and the valve V to produce a series of distinctive identificationdrilling fluid pressure pulses. Thus when switch arm 84 is positioned atstation S as indicated in Figure 4, there will be received andtranslated at the surface location a distinctive series of signalsindicating the position of the switch arm at station S5.

From the preceding descriptions it is evident that the driller oroperator at the surface location may by creating one or more temporaryreductions in pressure in the drilling fluid stream through appropriatemanipulation of lever 35 or valve 33, cause operation of the pressuredifferential responsive means comprising cylinder 44 and piston 44p inthe drill collar, and thus through operation of the step-by-stepcontroller means comprising ratchet wheel 53, activate any one of aplurality of information-securing units U1, etc. and cause informationof a selected type to be secured and information-representingpressure-increase signals to be transmitted from the subsurface locationto the surface location. If the position of switch arm 84 is not known,successive intermittent operation of the step-by-step means a number oftimes by appropriate operation of lever 35 or valve 33, will bring theswitch arm to station S5 and result in reception of the distinctive oridentification signal. The previous operating position of arm 84 maythen readily be determined by counting backward from station S5 thenoted number of stations. Also, from station S5 the subsurface apparatusmay be deactivated by initiating movement of arm 84 to station S0; andany one of the types of information secured by the subsurface apparatusmay then be obtained by effecting the proper number of temporarydrilling fluid pressure differential reductions.

The apparatus comprised in the information-securing units U1, etc. andin units 82, 85 and E1, etc., may be of any suitable desired type or maybe such as are disclosed in one or more of the aforementioned copendingapplications. Such units per se are not the present invention, andaccordingly may be selected from any available type suited to theenvironment and mode of operation of the invention as herein disclosed.Since in view of the disclosure, variations in the mode and apparatusspecifically herein described will occur to others skilled in the art,it is not desired to limit the invention to the specific details of thepreferred form of apparatus and operations described, except asindicated in the following claims and what is claimed is:

1. In asystem for obtaining at an accessible surface location outside anearth borehole information to be secured at a relatively inaccessiblesubsurface location in an earth borehole being drilled by meansincluding a rotary drill string, apparatus comprising: means to supplydrilling fluid under pressure to the drill string including means todecrease such pressure; and subsurface means for location within thelower end portion of the drill string, including step-by-step controllermeans, pressuresensitive means for operating the step-by-step controllermeans in response to a decrease in drilling fluid pressure followed byan increase in such pressure, and means rendered alternately active andinactive in response to stepping of the controller means for securinginformation and producing information-representing drilling fluidpressure increase signals in the drilling fluid for reception andtranslation at the surface location.

2. In a system for obtaining at an accessible surface location outsidean earth borehole, information to be secured at a relativelyinaccessible subsurface location in an earth borehole being drilled bymeans including a rotary drill string, apparatus comprising: means topump a stream of drilling fluid under pressure through the drill string,including means to decrease such pressure; stepby-step operating meansin said drill string for stepping in response to repetitive temporarypressure decreases in said drilling fluid stream; and means forincorporation in said drill string, rendered alternately active andinactive by said step-by-step operating means, for securing at saidsubsurface location information concerning a physical characteristic andfor there creating in the drilling fluid stream intermittent temporaryincreases in pressure representative of the secured information, andmeans for operation at said surface location for there detecting andtranslating the intermittent temporary increase in pressure to providethe secured information.

3. In a system for obtaining at an accessible surface location outsidean earth borehole, information to be secured at a relativelyinaccessible subsurface location in such borehole, apparatus comprising:a drill string extending between such locations; means at said surfacelocation for pumping through said drill string under pressure a streamof drilling fluid, including means for temporarily reducing pressure ofthe drilling fluid stream; means at said surface location sensitive totemporary pressure increases in said drilling fluid stream for sensingand recording translations of any such pressure increases; means in saiddrill string at said subsurface location sensitive to temporary pressuredecreases in said drilling fluid stream thereat; step-by-step meansoperated by said pressure-sensitive means at said subsurface location;and means in said drill string at said subsurface location renderedalternately active and inactive by step-by-step means, to there secureinformation concerning a physical characteristic and to produce in saiddrilling fluid stream intermittent temporary pressure increase signalsrepresentative of secured information, for reception and translation atsaid surface location to there provide the secured information.

4. In a system for obtaining at an accessible surface location outsidean earth borehole, information to be secured at a relativelyinaccessible subsurface location in an earth borehole, apparatuscomprising: a drill string; means for pumping a stream of drilling fluidunder pressure through the drill string, and including means at thesurface location for creating temporary reductions in pressure in thestream of drilling fluid; step-by-step movable means at said subsurfacelocation; pressure-sensitive controller means in the drill string foractuating said step-by-step movable means in response to temporaryreductions in pressure in the stream of drilling fluid; means at saidsubsurface location rendered alternately active and inactive by steppingof said step-by-step movable means, for there securing information andcreating intermittent temporary increases in pressure in the stream ofdrilling fluid representative of the secured information; and means atsaid surface location for detecting and translatinginformation-representing intermittent temporary increases in pressure inthe stream of drilling fluid; whereby said temporary increases inpressure are transmitted to said surface location for detection andtranslation to provide the secured information.

5. In a system for logging an earth borehole being drilled by meansincluding a drill string and a stream of drilling fluid flowing underpressure through the drill string, a subsurface apparatus comprising: asection of such drill string; means in said section includingpressure-sensitive means and step-by-step means operated thereby inresponse to successive temporary reductions in the pressure in thestream of drilling fluid stream thereat,

and means rendered alternately active and inactive by stepping movementsof said step-by-step means, and operative only when so rendered activeto derive logging information and create information-representingpressureincrease signals in the drilling fluid stream; whereby by saidcontrolled temporary reduction of pressure in the drilling fluid stream,logging of the borehole may be continued or discontinued at will.

6. Information securing and transmitting apparatus adapted forincorporation into a drill string in an earth borehole, comprising, incombination: a section of tubular drill string adapted to conveydrilling fluid under pressure therethrough; information-transmittingmeans in said section; pressure-sensitive means in said sectionresponsive to successive temporary reductions in the pressure of fluidin the section; means including a plurality of terminals and operablecontroller means movable in stepby-step order by said pressure-sensitivemeans in response to successive temporary reductions in the pressure offluid in said section; a plurality of information-securing units eachconnected to a respective one of said terminals; and means operated bysaid controller means for connecting each of said terminals in turn tosaid information-transmitting means, one terminal at each step, wherebyby repeated intermittent temporary reduction of pressure in saidsection, any selected one of said information-securing units may bebrought into connection with said information-transmitting means fortransmission of secured information.

7. In a system for obtaining at an accessible surface location outsidean earth borehole information to be secured at a relatively inaccessiblesubsurface location in an earth borehole being drilled by meansincluding a rotary drill string, apparatus comprising: means to supplydrilling fluid under pressure to the drill string including means todecrease such pressure; and subsurface means for location within thelower end portion of the drill string, including step-by-step controllermeans, pressuresensitive means for operating the step-by-step controllermeans in response to a decrease in drilling fluid pressure followed byan increase in such pressure, and means rendered selectively active andinactive in response to stepping of the controller means for securinginformation and producing information-representing drilling fluidpressure increase signals in the drilling fluid for reception andtranslation at the surface location.

References Cited in the file of this patent UNITED STATES PATENTS2,388,141 Harrington Oct. 30, 1945 2,677,790 Arps May 4, 1954 2,700,131Otis et al. Jan. 18, 1955 2,700,897 Arps Feb. 1, 1955

